Alterations of heart muscle Z-disc structure have been reported in congestive heart failure, cardiac hypertrophy, in older hearts, and in the normal myocardium during growth periods. In addition, skeletal muscle Z discs of abnormal appearance have been reported in a variety of myopathies. Unfortunately there exists a paucity of knowledge pertaining to Z-discs, and the significance of the presence of the altered structures in striated muscle remains obscure. Accordingly, the major emphasis of the research program will be to obtain basic information regarding structural and chemical properties of Z-discs from several species, including cats, dogs and pigeons. Since the techniques for isolationg Z-discs from muscle tissue have been recently perfected in my laboratory, particular attention will be paid to the study of isolated discs, and to the comparison of their properties with those of non-isolated in vivo discs. Z-disc extraction and reconstitution studies will be performed as will immunological studies. Such investigation will be done both in vivo and isolated discs, from both normal muscle and from muscle displaying abnormal Z- discs. It is anticipated that the research will yield considerable basic information about myocardial and skeleltal muscle Z-discs, and give insight into the nature of the Z alterations which occur in certain pathological conditions.